1. Field of Industrial Utilization
The invention relates to a dc power supply circuit and improvements in on a return circuit thereof.
2. Description of the Related Arts
A conventional dc power supply circuit such as the feeder circuit disclosed in JP A 56-124520 is constructed in a looped power supply circuit, connecting a plurality of dc circuit breakers to a plurality of diodes, and connected again to rectifiers of the diodes through an electric railcar in contact with a feeder connected to each dc circuit breaker and rails.
In recent years, the performance of semi-conductor elements such as diodes, thyristers, etc. has improved remarkably and, as they are being made lower in loss and larger in capacity, an accident current flows instantaneously (such as an accidential) when short circuit occurs in a dc power supply circuit, circuit containing the semi-conductor element, for instance. The accident current has a characteristic curve A as shown in FIG. 2, and is remarkably larger than an interruption current B of a dc circuit breaker.
As a result, it is impossible to interrupt the current without use of a dc circuit breaker of large interruption capacity, which requires the dc circuit breaker to be made larger. Morever, in an existing dc power supply circuit it may be necessary to be replaced the circuit breaker with a dc circuit breaker of large capacity.